Color electrophotographic printing machine

ABSTRACT

A color electrophotographic printing machine in which a black and white copy or a color copy may be formed from an original document. In one mode of operation, the printing machine produces a black and white copy by employing black toner particles therein. An alternate mode of operation creates a color copy through the combination of cyan and red toner particles. The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it intended to be limiting to the scope of the invention in any way.

United States Patent [1 1 Lehmann [111, 3,869,203 [451' Mar. 4, 1975 1 COLOR ELECTROPHOTOGRAPHIC PRINTING MACHINE [75] Inventor: Ernest H. Lehmann, Arcadia, Calif.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Sept. 18, 1973 211 Appl. No.: 398,342

[52] US. Cl. 355/4 [51] Int. Cl G03g 15/00 [58] Field of Search 355/3, 4

[56] References Cited UNITED STATES PATENTS 3,532,422 10/1970 McFarlane 355/4 3,627,410 12/1971 Jugle 355/4 3,661,452 5/1972 Hewes 355/3 3,724,943 4/1973 Draugelis 355/4 Primary Examiner-John M. Horan Attorney, Agent, or Firm-H. Fleisher; C. A. Green; J. J. Ralabate [57] ABSTRACT A color electrophotographic printing machine in which a black and white copy or a color copy may be formed from an original document. In one mode of operation, the printing machine produces a black and white copy by employing black toner particles therein. An alternate mode of operation creates a color copy through the combination of cyan and red toner particles.

The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it intended to be limiting to the scope of the invention in any way.

18 Claims, 8 Drawing Figures PATENTED 4|975 3.869203 sum 1 95 g PATENTEUHAR 41% 3.869203 sum 2 95 z PATENTEUHAR 1975 sum u or 8 PATENTEU W 4 I975 SHEET 7 [IF 8 COLOR ELECTROPHOTOGRAPHIC PRINTING MACHINE BACKGROUND OF THE INVENTION This invention relates generally to color electrophotographic printing, and more particularly concerns a new printing technique for accomplishing color printing or black and white printing on the same machine readily in a simple and continuous manner.

The process of electrophotographic printing com prises exposing a charged photoconductive member to a light image of an original document. The irradiated areas of the photoconductive surface are discharged to record thereon an electrostatic latent image corresponding to the original document. A development system, thereupon, moves a developer mix of carrier granules and toner particles into contact with the photoconductive surface. Toner particles are attracted electrostatically to the latent image from the carrier granules to thereby form a toner powder image on the latent image. Then, the toner powder is transferred to a sheet of support material. After the toner powder image has been transferred to the sheet of support material, the sheet of support material advances to a fuser which permanently affixes the toner powder image thereto.

Essentially, multi-color printing repeats the foregoing process a plurality of cycles. For example, US. Pat. No. 3,53l,l95 issued to Tanaka, et al. in 1970 discloses a multi-color electrophotographic printing machine. As recited therein, the light'image is filtered to record an electrostatic latent image on the photoconductive surface corresponding thereto. The electrostatic latent image is then developed with toner particles complementary in color to the filtered light image. The toner powder image is then transferred to the sheet of support material. The foregoing process is repeated for successively differently colored light images. In this manner, a plurality of toner powder images are transferred to the sheet of support material, in superimposed registration with one another. Each of the toner powder images are complementary in color to the color of the filter utilized to produce the light image projected onto the photoconductive member. As described in Tanaka, each toner powder image is fused after being transferred to the support material. However, it is not necessary to implement this type of procedure, but rather, all of the toner powder images may be fused simultaneously after they have been transferred to the support material. It should be noted that black is a process black wherein it is created by a combination of all the subtractive toner powder images. At no time in the foregoing technique is black, in and of itself, deposited on the support material. Thus, black may be viewed as a combination of all the respective subtractive toner particles deposited on the support material. Therefore, it is evident, that in order to reproduce a black and white original on a color printing machine of this type, the copy must undergo the normal plurality of processes wherein each cycle produces one of the subtractive colors contained in'black. Thereafter, all of these subtractive colors, as represented by the respective toner particles, are fused to one another forming a black corresponding to the original document. In no manner does the machine have the capability of reproducing black in and of itself.

Accordingly, it is the primary object of the present invention to improve color electrophotographic printindependent of color capability.

SUMMARY OF THE INVENTION Briefly stated, and in accordance with the present invention, there is provided an electrophotographic printing machine adapted to produce black and white copies or color copies from an original document.

Pursuant to the present invention there is provided a photoconductive member which is charged to a substantially uniform level. The charged photoconductive member is exposed to a light image of the original document recording an electrostatic latent image thereon. The light image is color filtered when a color copy is being produced. Contrawise, the light image is not color filtered when a black and white copy is being reproduced. The electrostatic latent image is developed with toner particles. When the light image is filtered, the electrostatic latent image is developed with toner particles complementary in color to the filtered light image. An electrostatic latent image created, from a non-filtered light image is developed with black toner particles. The toner powder image adhering to the electrostatic latent image is transferred to a sheet of support material. Subsequently, the toner powder image is fused to the sheet of support material.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to thedraw ings, in which: I

FIG. 1 is a schematic perspective view of the color electrophotographic printing machine of the present invention;

FIG. 2 is a perspective view of the corona generating apparatus employed in the FIG. 1 printing machine to charge the photoconductive drum therein;

FIG. 3 is a schematic illustration of the optical system of the FIG. 1 printing machine;

FIG. 4 is a sectional elevational view of the development system used in the FIG. 1 printing machines;

FIG. 5 is a fragmentary, sectional elevational view depicting, in detail, one of the developer units shown in the FIG. 4 development system;

' FIG. 6 is a schematic perspective view of the transfer system employed in the FIG. 1 printing machine;

FIG. 7 is a perspective view of the FIG. 1 printing machine fuser; and

FIG. 8 is a sectional elevational view of the FIG. 7 fuser lower housing.

While the present invention will hereinafter be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION For a general understanding of the disclosed color electrophotographic printing machine of the present invention, continued reference is had to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. Initially, the overall process for producing the black and white 3 copies or color copies will be described with reference to FIG. 1. Thereafter, the detailed structural configuration of the various sub-assemblies utilized in the FIG. 1 printing machine will be discussed, in detail. Although the color electrophotographic printing machine of the present invention is particularly well adapted for producing black and white copies, it should become evident from the following discussion that it is equally well-suited for producing color copies and is not necessarily limited to the particular materials described herein.

As depicted in FIG. 1, the electrophotographic printing machine employs a photoconductive member having a drum mounted rotatably within the machine frame (not shown). Photoconductive surface 12 is mounted on the exterior circumferential surface of drum 10. One type of suitable photoconductive material is disclosed in US. Pat. No. 3,655,377 issued to Sechak in l972. A series of processing stations are disposed such that as drum 10 rotates in the. direction of arrow 14 it passes sequentially therethrough. Drum 10 is driven at a predetermined speed relative to the other machine operating mechanisms from a common drive motor (not shown). A timing disc mounted in the region of one end of the shaft of drum 10 cooperates with the machine logic to synchronize the various operations with the rotation of drum 10. In this way, the proper sequence of events is produced at the respective processing stations.

Initially, drum 10 rotates photoconductive surface 12 through charging station A. At charging station A, a corona generating device, indicated generally at 16, extends longitudinally in a transverse direction across photoconductive surface 12. Corona generating device 16 will be described hereinafter, in greater detail, with reference to FIG. 2. This readily enables corona generating device 16 to spray ions onto photoconductive surface 12 producing a relatively high, substantially uniform charge thereon.

After photoconductive surface 12 is charged to a substantially uniform potential, drum 10 is rotated to exposure station B. At exposure station B, a color filtered light image of original document 22 is projected onto charged photoconductive surface 12. However, if a black and white copy is desired, a non-colorfiltered light image of original document 22 is projected onto photoconductive surface 12. Of course, a neutral density filter may be employed for exposure corrections or a yellow filter may be utilized to enhance blue ink renditions. Exposure station B includes a moving lens system, generally designated by the reference numeral 18, and a color filter mechanism shown generally at 20. Original document 22, such as a sheet of paper, book, or the like is placed face down on transparent viewing platen 24. As shown in FIG. 1, lamps 26 are adapted to move in timed relation with lens 18 and filter mechanism 20 to scan successive incremental areas of original document 22 disposed upon platen 24. In this manner, a flowing light image of original document 22 is projected onto photoconductive surface 12. If a color copy is being reproduced, filter mechanism 20 interposes selected color filters into the optical path of lens 18 during the exposure process. The appropriate filter operates on the light rays transmitted through lens 18 to record an electrostatic latent image on photoconductive surface 12 corresponding to a preselected spectral region of the electromagnetic wave spectrum, hereinafter referred to as a single color electrostatic latent image. Contrawise, if a black and white copy is being created, no color filter operates on the light rays and a noncolor filtered electrostatic latent image is recorded on photoconductive surface 12. The exposure system will be discussed in greater detail with reference to FIG. 3.

After the electrostatic latent image is recorded on photoconductive surface 12, drum 10 rotates to development station C. At development station C, three individual developer units, generally indicated by the reference numeral 28, 30 and 32, respectively, are arranged to render visible the electrostatic latent image recorded on photoconductive surface 12. Preferably, the developer units are all of a type generally referred to in the art as magnetic brush developer units. Typical magnetic brush systems utilize a magnetizable developer mix which includes carrier granules and toner particles. Generally, the toner particles are heat settable. In operation, the developer mix is continually brought through a directional flux field to form a brush thereof. The electrostatic latent image recorded on photoconductive surface .12 is brought into contact with the brush of developer mix. Toner particles are attracted from the developer mix to the latent image.

Each of the developer units contain appropriately colored toner particles. For example, a non-color filtered electrostatic latent image is developed by depositing black toner particles thereon. A cyan filtered latent image is developed with red toner particles, and a red filtered latent image is developed with cyan toner particIe's'The development system employed in the FIG. 1 printing machine will be discussed in greater detail with reference to FIGS. 4 and 5.

Drum 10 is next rotated to transfer station D where the powder image adhering electrostatically to photoconductive surface 12 is transferred to a sheet of final support material 34. Support material 34 may be plain paper of a sheet of thermal plastic material, amongst others. Transfer station D includes corona generating means, indicated generally at 36, and a transfer member, designated generally by reference numeral 38. Corona generator 36 is excited with an alternating current and is arranged to pre-condition the toner powder image adhering electrostatically to photoconductive surface 12. In this manner, the pre-conditioned toner powder image will more readily be transferred from the electrostatic latent image recorded on photoconductive surface 12 to support material 34 by transfer member 38. Transfer member 38 is a roll adapted to recirculate support material 34 and is electrically biased to a potential of sufficient magnitude and polarity to attract electrostatically the preconditioned toner particles from the latent image recorded on photoconductive surface 12 to support material 34. Transfer roll 38 rotates in synchronism with drum 10 to maintain the electrostatic latent image recorded on photoconductive surface 12 in registration with support material 34 secured releasably thereto. Inasmuch as support material 34 is secured releasably on transfer member 38 for movement in a recirculating path therewith, successive toner powder images may be transferred thereto in superimposed registration with one another. In this case, transfer roll 38 rotates, in the direction of arrow 40, at substantially the same angular velocity as drum 10. Corona generator 36 and transfer member 38 will be described hereinafter in greater detail with reference to FIG. 6.

Support material 34 is advanced from a stack 42 thereof mounted on tray 44. Feed roll 46, in operative communication with retard roll 48, advances and separates the uppermost sheet from stack 42. The advancing sheet moves into chute 50 which directs it into the nip between register rolls 52. Thereafter, gripper fingers, indicated generally at 54, mounted on transfer roll 38 secure releasably thereon support material 34 for movement in a recirculating path therewith. After the requisite number of toner powder images (one in the case of a black and white copy, two in the case of a color copy) have been transferred to support material 34, gripper fingers 34 release support material 34 and space it from transfer roll 38. Stripper bar 56 is then interposed therebetween to separate support material 34 from transfer roll 38. Thereafter, endless belt conveyor 58 advances support material 34 to fixing station E. At fixing station E a fuser, indicated generally at 60, coalesces the transferred powder image to support material 34. Fuser 60 will be described hereinafter, in greater detail, with reference to FIGS. 7 and 8. After the fusing process, support material 34 is advanced by endless belt conveyors 62 and 64 to catch tray 66 permitting subsequent removal therefrom by the machine operator.

Although a preponderance of the toner particles are transferred to support material 34, invariably some residual toner particles remain on photoconductive surface 12 after the transfer of the powder image therefrom. Residual toner particles are removed from the photoconduetive surface 12 as it moves through cleaning station E. Here, the residual toner particles are first brought under the influence of a cleaning corona generating device (not shown) adapted to neutralize the electrostatic charge remaining on the residual toner particles and photoconduetive surface 12. The neutralized toner particles are then cleaned from photocon' ductive surface 12 by a rotatably mounted fibrous brush 68 in contact therewith. A suitable brush cleaning device is described in US. Pat. No. 3,590,412 issued to Gerbasi in 1971. Hence, residual toner particles remaining on photoconductive surface 12, after each transfer operation, are readily removed therefrom.

It is believed that the foregoing description is sufficient for purposes of the present application to depict the general operation of the color electrophotographic printing machine of the present invention.

Referring now to the specific subject matter of the various sub-assemblies, FIG. 2 depicts corona generating apparatus 16. Corona generating apparatus 16 includes an elongated conductive shield 70 defining an open-ended chamber opposed from and closely spaced to photoconduetive surface 12. Shield 70 is a U-shaped housing and, preferably, is made from an aluminum extrusion. A plurality of substantially parallel spaced, fine conductive wires 72 (in this case extend in a longi tudinal direction from one end of shield 70 to the other end thereof and across about three quarters of the open end of the chamber therein. An insulating plate 74 is affixed permanently to both ends of shield 70 by a suitable means (not shown), e.g., fasteners. Interposed between grid wires 72 and backwall 76 of shield 70 is a pair of coronode wires 78 and 80, respectively. (Zoronode wires 78 and 80 are suitably secured to insulating plate 74, preferably, by fasteners (not shown). Both grid wires 72 and coronode wires 78 and 80, respectively, are, preferably, made from a conductive material, for example, platinum. Insulating plate 74 is, preferably, made from a dielectric material such as a glass alkyd, polycarbonate plastic, polymethylmethacrylate plastic, or the like. As illustrated in FIG. 2, coronode wire 80 is positioned in the chamber of shield that is not covered by grid wires 72, i.e., grid wires 70 do not extend over this portion of the open end of shield 70. As hereinbefore mentioned, grid wires 72 extend only across about three quarters of the open end of shield 70. This permits rapid and roughly controlled charging of photoconduetive surface 12 in the lead section or the portion of shield 70 not covered by grid wires 72. Slow and well controlled charging is obtained over the trailing section or portion of the shield 70 covered by grid wires 72. A high voltage source (not shown) excites coronode wires 78 and to a voltage preferably ranging from about 6,000 volts to about 8,000 volts, the coronode current ranging from about 200 to about 500 micro-amps. A low voltage source (not shown) excites gridwires 72 to, preferably, about 800 volts.

In order to reduce the sensitivity of corona generating apparatus 16 to contamination, deposits of toner particles and dust collected on coronode wires 78 and 80, respectively, and grid wires 72 are removed therefrom by wiper member 82. Wiper member 82 is, preferably, formed of a slightly abrasive material such as felt, foam, or expanded polyester. Moving means or a support carriage, generally indicated at 84 reciprocates wiper member 82 along coronode wires 78 and 80 and grid wires 72. Support carriage 84 includes an elongated rod 86 attached to support 88. Rod 86 extends through insulating plate 74. Preferably, rod 86 extends longitudinally through the center of shield 70. In this manner, an operator may grasp rod 86 to reciprocate wiper member 82 in a longitudinal direction. This causes wiper member 82 to remove dust particles from coronode wires 78 and 80, as well as grid wires 72. Corona generating device 16 is described in greater detail in co-pending application Ser. No. 307,250 filed in 1972, the disclosure of which is hereby incorporated into the present application.

Turning now to FIG. 3, exposure station B is described therein in greater detail. Lamp carriage 90 supports a pair of light sources or lamps 26 thereon. Lamp carriage 90 is arranged to traverse platen 24 illuminating incremental width of original document 22 disposed thereon. Lamp carriage 90 is mounted by suit able means and driven by a cable pulley system from drive motor 152 (FIG. 6) driving drum 10. As lamp carriage 90 traverses platen 24, another cable pulley acts to also move lens 18 at a correlated speed therewith on suitable rollers surrounding a shaft (not shown). Filter assembly 20 is mounted by a suitable bracket on lens 18 to move therewith. Lamps 26, lens 18, and filter 20 scan original document 22 to create a flowing light image thereof. When a black and white copy is desired, filter mechanism 20 does not interpose a color filter into the optical light path. In this way, a light image of the original document is created by lens 18 and is projected onto photoconductive surface 12. Contrawise, if a color copy is being reproduced, filter 20 will interpose selected color filters to create a single color electrostatic latent image on photoconduetive surface 12. Upon reaching the end of the path of scan, platen 24, lens 18, and filter 20 are spring biased to return to their original position for the start of the next cycle. Similarly, lamps 26 return to their original position for the start of the next cycle. It should be clear that the movement of lens 18, filter 20, and lamps 26 is correlated with the speed of rotation of drum 10 for exposure of photoconductive surface 12. For greater details regarding the optical system described in FIG. 2 and its cooperation with the movement of drum 10, reference is made to U.S. Pat. No. 3,062,109 issued to Mayo, et al. in 1962. It should be noted that mirror 92 reflects the light rays reflected from original document 22 through lens 18. After passing through lens 18, the light rays are transmitted through filter 20. Thereafter, the light rays are reflected from a second mirror 94 onto photoconductive surface 12 of drum 10 to selectively dissipate the charge thereon in the irradiated areas to form an electrostatic latent image. If a color filter is utilized, i.e. in the case of a color copy being formulated, an electrostatic latent image is recorded thereon corresponding to a single color in the original document. Contrawise, in the case of a black and white copy being reproduced, the electrostatic latent image recorded on photoconductive surface 12 corresponds to the complete original document.

Preferably, lens 18 is a six-element, split dagor type of lens system having front and back compound lens components with a centrally located diaphragm therebetween. The lens system forms high-quality images with a field angle of 3l and a speed of F4.5 at a 1:1 magnification. In addition, the lens is designed to minimize the effect of secondary color at the image plane. The front lens component has three lens elements including in the following order, a first lens element of positive power, a second lens element of negative power cemented to the first lens element, and a third lens element of positive power disposed between the second lens element and diaphragm. The back lens component also has three similar lens elements positioned so that lens 18 is symmetrical. In a specific embodiment of the lens, the first lens element in the front component is a double convex lens, the second element, a double concave lens, and the third element a convex-concave lens element. For greater details regarding lens 18, reference is made to U.S. Pat. No. 3,592,531 issued to McCrobie in 1971 the disclosure of which is hereby incorporated into the present application.

Referring once again to FIG. 3, filter 20 includes a housing which is mounted on lens 18 by a suitable bracket and moves with lens 18 during scanning as a single unit. The housing of filter 20 includes a window which is positioned relative to lens 18 to allow the light reflected from original document 22 on platen 24 to pass therethrough. Bottom and top walls of the housing member include a plurality of tracks which extend the entire width thereof. Each track is adapted to carry a filter and filter frame in a manner to allow movement of the filter from an inoperative position to an operative position interposed in the window of the housing to allow the light rays to pass therethrough. The individual filters are mounted in a frame and made of any suitable filter material, such as coated glass. The number of color filters utilized in the electrophotographic printing machine of FIG. 1 is two. The filters are biased into a position to be inserted into the window of the housing member by individual extension springs. When not in operation, the two color filters of filter 20 are retained in an inoperative position. The color filters are locked into position out of line of the housing window by means of a stop pin which extends up through an opening in the bottom of the housing into the respective track of each filter. A solenoid arm in association with the stop pin retains the filters in the inoperative position. A selected color filter is inserted into the optical path of the housing window by activation of the appropriate solenoid. By activating the selected solenoid, the respective stop pin is moved downward away from the path of the appropriate filter, thereby allowing the springs cooperating with the filter to pull the filter into the optical path of the housing window. When a filter is activated into an operative position in the housing window, the filter will remain there throughout the entire scanning of the original document. As previously indicated, lens '18, and filter 20 are adapted to return to the starting'position by suitable springs upon completion of scanning of the original document 22. During the return of the system to the initial position, the first color filter is removed from the operative positionand the second color filter inserted therein. Preferably, filter mechanism 20 includes two color filters, a cyan filter and a red filter. Each of the filters is associated with its respective toner particles, i.e., the complement of the color thereof to produce a subtractive system. A cyan filtered light image is developed with red toner particles and a red filtered light image is developed with cyan toner particles. When no color filter is interposed into the optical light path, the electrostatic latent image is developed with black toner particles.

Referring now to FIGS. 4 and 5, the development system of the FIG. 1 electrophotographic printing machine will be described in detail. As shown in FIG. 4, frame 96 supports three toner depositing means or development units 28, 30 and 32, respectively. The aforementioned development system is of the type utilized at station C. These development units are depicted in an elevational sectional view to indicatemore clearly the various components included therein. Only development unit 28 will be described in'detail as development units 30 and 32 are nearly identical thereto, the distinction between each developer unit being the color of toner particles contained therein and minor geometrical differences due to the mounting arrangement. Developer unit 28 may have black toner particles, unit 30 cyan toner particles, and unit 32 red toner particles. For purposes of explanation, developing unit 28 will hereinafter be described in detail.

The principle components of developer unit 28 are developer housing 98, conveyor means or paddle wheel 100, transport means or roll 102, and developer means or roll 104. Paddle wheel 100 is a cylindrical member with buckets or scoops around the periphery thereof and is adapted to rotate so as to elevate developer mix 106 from the lower region of housing 98 to the upper region thereof. When developer mix 106 reaches the upper region of housing 98, it is lifted from the paddle wheel buckets to transport roll 102. Alternate buckets of paddle wheel 100 have apertures in the root diameter so that the developer mix in these areas is not carried to transportroll 102, but, instead, falls back to the lower region of developer housing 98. As the developer mix falls back to the lower region of developer housing 98, it cascades over shroud 108 which is of a tubular configuration with aperture 110 in the lower region thereof. Developer mix 106 is recirculated in this manner so that the carrier granules are continually agitated to mix with fresh toner particles. This generates a strong triboelectric charge between the carrier granules and toner particles. As developer mix 106, in the paddle wheel buckets, approaches transport roll 102, the magnetic fields produced by the fixed magnets therein attract developer mix 106. Transport roll 102 moves developer mix 106 in an upwardly direction by the frictional force exerted between the roll surface and developer mix. A surplus of developer mix is furnished, and metering blade 112 is provided to control the amount of developer mix carried over the top of transport roll 102. The surplus developer mix 106 is sheared from transport roll 102 and falls in a downwardly direction toward paddle wheel 100. As the surplus developer mix descends, it falls through the apertures of paddle wheel 100 in a downwardly direction into the lower region of developer housing 98. The developer mix which passes metering blade 112 is carried over transport roll 102 to developer roll 104 and into development zone 114 located between photoconductive surface 12 and developer roll 104. The electrostatic latent image recorded on photoconductive surface 12 is developed by contacting the moving developer mix 106. The charged areas of photoconductive surface 12 electrostatically attract the toner particles from the carrier granules of developer mix 106. Upon passing from the development zone, the unused developer mix and denuded carrier granules enter a region relatively free from magnetic forces and fall from de veloper roll 104 in a downwardly direction in the lower region of developer housing 98. As the unused developer mix and denuded carrier granules descend, they pass through mixing baffle 116 which diverts the flow from the ends toward the center of developer housing 98 to provide mixing in this direction.

Turning now to FIG. 5, the operation of developer unit 28 will be discussed in detail. Developer housing 98 is pivoted about the center of paddle wheel 100 and is supported at the lower region of the exterior surface by rollers 118 and 120 mounted rotatably in frame 96. Biasing means or spring 122 pivots developer housing 98 against stop 124. In this position, developer roll 104 is in its non-operative position spaced from photoconductive surface 12. Operation begins when clutch gear 126 meshes with gear 128 which is attached to paddle wheel 100, thereby causing paddle wheel 100 to revolve clockwise as indicated by arrow 130. As gear 128 and paddle wheel 100 start to rotate, a reaction torque is exerted against developer housing 98 due to the resistance to motion of developer mix 106 which fills developer housing 98. This reaction torque causes housing 98 to rotate clockwise against the force of spring 122 until a stop, shown as a wheel 132, is positioned against drum 10. Rolls 102 and 104 are rotated in conjunction with paddle wheel 100 by a gear train (not shown). When the latent image recorded on photoconductive drum has passed development zone 114, development action is discontinued and the developer mix removed from contact with photoconductive surface 12. To achieve this, the drive motor is disconnected from gear 126 by de-energizing the clutch leaving gear 126 free to turn in either direction. Paddle wheel 100, developer roll 104, and transport roll 102 stop rotating, and developer housing is pivoted clockwise by spring 122 until it engages stop 114 in its inoperative position. This completes the cycle.

The aforementioned procedure has been described for developer unit 28, however, this procedure is repeated for developer units 30 and 32, respectively. In the formation of a black and white copy, only developer unit 28 is positioned into contact with the nonfiltered electrostatic latent image. However, in the formation of a color copy, initially developer unit 30 is positioned in contact with the single color electrostatic latent image, and thereafter, developer unit 32 is positioned in contact with its respective single color electrostatic latent image.

In the preferred embodiment thereof, developer means or roll 104, as best shown in FIG. 5, includes a non-magnetic tubular member 134, preferably made from an aluminum tube having an irregular or roughened exterior surface. Tubular member 134 is journaled for rotation by suitable means such as ball hearing mounts. A shaft 136 made, preferably, of steel is mounted within tubular member 134 and serves as a fixed mounting for magnetic means 138. Magnetic means 138, preferably, includes magnets made of barium ferrite in the form of annular rings and is arranged with five poles on about a 284 are about shaft 136.

Similarly, transport means or roll 102 includes a nonmagnetic tubular member 140, also, preferably made from an aluminum tube having an irregular or roughened exterior surface. Tubular member is journaled for rotation by suitable means such as ball bearing mounts. A shaft 142, preferably made of steel is concentrically mounted within tubular member 140 and functions as a fixed mounting for magnetic means 144. Magnetic means 144, preferably, includes barium ferrite magnets in the form of annular rings arranged with four poles on about a 180 are about shaft 142. Each of the toner depositing means or developer units 28, 30 and 32, respectively, is actuated by the timing disc (not shown) mounted on the shaft of drum 10. The timing disc is opaque with a plurality of spaced slots in the circumferential periphery thereof. The timing disc is interposed between an illuminating source and a photosensor to generate an electrical signal as each slot permits light rays to pass through the disc. The electrical signal, in association with a suitable machine logic control system, activates the appropriate developer unit. For example, if the machine operator presses the button indicating that only a black and white copy is to be reproduced, the timing disc, in association with the machine logic, will only actuate developer unit 28. Contrawise, if the machine operator depresses the button indicating that a color copy is to be reproduced, the timing disc in association with the machine logic will activate developer units 30 and 32, while maintaining developer unit 28 inactive. Activation of the respective developer unit energizes the drive motor which rotates the paddle wheel, transport roll and developer roll producing a reaction torque which overcomes the spring restraining force, wherein the developer roll is moved into operative communication with the photoconductive surface. After the photoconductive surface has roated through an appropriate angle, a slot in the timing disc permits the light rays from the illumination source to once again cause the photosensor to generate a second electric signal, which, in association with the machine logic, deactivates the developer unit by deenergizing the drive motor. Inactivation of the developer unit automatically causes the developer unit to be moved to the inoperative position, wherein the developer roll is biased from the photoconductive surface. The development system discussed heretofore is disclosed in co-pending application Ser. No. 255,259, filed in 1972, the disclosure of which is incorporated into the present application.

Turning now to FIG. 6, the structural arrangement of transfer station D is described therein in detail. Transfer roll 38 includes an aluminum tube 146, preferably having a'% inch thick layer of urethane 148 cast thereabout. A polyurethane coating 150, preferably of about 1 mil thick, is sprayed over the layer of cast urethane 148. Preferably, transfer roll 38 has a durometer hardness ranging from about units to about 30 units on the Shore A scale. The resistivity of transfer roll 38, preferably, ranges from about 10 to about 10 ohmcentimeters. A direct current bias voltage is applied to aluminum tube 146 by suitable means, such as a carbon brush and brass ring assembly (not shown). The transfer voltage may range from about 1,500 to about 4,500 volts. Transfer roll 38 is substantially the same diameter as drum 10 and is driven at substantially the same angular velocity. Contact between photoconductive surface 12 of drum 10 and transfer roll 38 with support material 34 interposed therebetween, is preferably limited to a maximum of about 1.0 pounds linear force. Preferably, transfer roll 38 includes a pair of tapered end bells which are secured to one another by three tie rods. A compression spring limits the tension of the tie rods to about 10 pounds. A pair of spring loaded pivot arms is located on a stationary shaft support transfer roll 38 in the electrophotograpic printing machine. Solenoids. and secondary springs (loaded to about 0.02 pounds per linearinch) lift transfer roll 38 with support material 34 secured thereon against photoconductive surface 12 of drum 10. Transfer roll 38 is moved approximately one-eighth inch in order to engage photoconductive surface 12. A spring loaded yoke supports transfer roll 38. This yoke is articulated to permit transferrol 38 to be positioned about its own centerline and the centerline drum 38. The drive is coupled directly to transfer roll 38 by flexible metal bellows 152 which permits the lowering and raising of transfer roll 38. Synchronization of transfer roll 38 and drum 10 is accomplished by precision gears (not shown) coupling the main drive motor to both transfer roll 38 and drum 10.

With continued reference to FIG. 6, corona generator 36 includes an elongated shield 154 made from a conductive material such as an aluminum extrusion. Elongated shield 154 is substanially U-shaped and may be grounded or, in lieu thereof, biased to a suitable electrical voltage. A discharge electrode 156 is mounted in the chamber designed by U-shaped shield 154. discharge electrode 156 is, preferably a coronode wire approximately 0.0035 inch in diameter and ex tends longitudinally along the length of shield 154. Coronode wire 156 is preferably made from platinum. Coronode wire 156 is excited so as to produce a flow of ions therefrom. The ion flow is adapted to precondition the toner particles deposited on the electrostatic latent image of photoconductive surface 12. In this way, the efficiency of transfer roll 38 is enhanced so as to attract the toner powder image more readily from the electrostatic latent image recorded on photoconductive surface 12. When the toner particles are pre-conditioned in the foregoing manner, substantially the entire toner powder image is transferred therefrom. Preferably, discharge electrode 156 is excited at about 110 micro-ampres and at about 4,400 volts rms, the

range being from about micro-amperes at about 3,000 volts rms to about 200 micro-amperes at about 5,000 volts rms. The alternating current output from coronode wire 156 to photoconductive surface 12 with the toner powder image thereon ranges from about 3.0 to about 5.0 micro-amperes, and is preferably about 4.0 micro-amperes. The foregoing arrangement for transferring the toner image to the sheet of support material is described in co-pending application Ser. No. 335,968, filed in 1973, the disclosure of which is hereby incorporated into the present application.

Referring now to FIGS. 7 and 8, fuser 60 will be described hereinafter in greater detail. Fuser 60 is depicted in FIG. 7 as having the cover member 158 pivoted to an open position. Conveyor 58 is associated with fusing apparatus 60 to transport support material 34 from transfer roll 38 thereto. Conveyor 58 includes a plurality of endless belts 160 entrained about a pair of opposed spaced rollers 162. A vacuum system maintains a low pressure by drawing air through apertures 164 of belt 160 to tack support material 34 thereto. Cover member 158 includes radiant energy source 166. Lower housing member 168 defines an open-ended chamber having a pair of spaced rolers 170 and 172 mounted rotatably on a transport frame disposed therein. An endless belt 174 is entrained about rollers 170 and 172. Endless belt 174 includes a plurality of apertures 176 therein which are arranged to draw air therethrough such that support material 34 is tacked thereto as it passes through fuser 60. Preferably, cover member 158 includes a sheet metal shell having secured to the interior surface thereof suitable insulation. A nylon fiber coating is sprayed on the exterior surface of cover member 158 to protect the operator. An outer reflector is suitably attached to the insulation secured to the interior surface ofthe cover metal shell. An inner reflector is mounted on the outer reflector. As mounted, the inner and outer reflectors are spaced from one another permitting air to circulate therebetween. A thermistor is positioned in the air space between the inner and outer reflectors to measure the temperature thereat.

Radiant energy source 166 is preferably a radiant heat strip made from a nickel chromium alloy ribbon entrained helically about a par of opposed spaced support members, such as ceramic spools. Heat strip 166 is arranged to provide substantially uniform radiation. A suitable guide, preferably quartz woven string, is wound heat strips 166 and adapted to prevent support material 34 from contacting it.

Turning now to FIG. 8, there is shown a sectional view of lower housing assembly 168. Lower housing 168 includes a sheet metal shell having insulation secured to the interior surface thereof. The transport frame is mounted removably in the shell. Rollers 170 and 172 are mounted rotatably on the frame and have entrained thereabout endless belt 174. Interior surface 174b of endless belt 174 is adapted to be closely adjacent to plate member 178. Plate member 178 is adapted to be heated by air moving in the direction of arrow 180. Blower member 182 has a vaned member 184 mounted thereon to produce an air flow in the direction of arrows 180. The air flow passes over heating means or auxiliary heater 186 onto plate member 178 raising the temperature thereof. Plate member 178 is closely adjacent to under surface 174b of endless belt 174 and transmits heat thereto. This, in turn, raises the temperature of support material 34 minimizing any heat loss therefrom. In this manner, radiant energy from heat strips 166, in conjunction with auxiliary heater 186 fuses the toner powder image formed on support material 34.

Auxiliary heater 186 is preferably a 800 watt tubular heater. A thermistor is arranged to detect the temperature of endless belt 174. The thermistor is mounted on a thermally conductive shoe which, in turn, is adapted to contact lower surface 174b of belt 174. Preferably, blower motor 182 is a two-pole split capacitor motor and is adapted to maintain a pressure differential of suitable magnitude to tack support material 34 to the exterior surface 174a of endless belt 174. As hereinbefore mentioned, a suitable timing disc mounted on drum and adapted to rotate therewith, cooperates with the machine logic to actuate fusing apparatus 60 when sheet 34 passes therein.

In operation, the electrophotographic printing machine of FIG. 1 is energized and heated from a cold condition to a stand-by condition. During the warm-up phase both auxiliary heater 186 and radiant energy source 166 operate at full power of about 1,750 watts. When endless belt 174 is raised to a pre-selected standby condition which may range from about 390F to about 420F, depending upon humidity conditions, radiant energy source 166 is de-energized. Fuser 60 is maintained at the stand-by temperature by auxiliary heater 186. When a sheet of support material 34 enters fuser 60, the machine logic energizes radiant energy source 166 at the upper power level (in this case 1,750 watts) and de-energizes auxiliary heater 186. As the sheet of support material 34 exits fuser 60, the machine logic energizes auxiliary heater 186 and de-energizes radiant energy source 166. The preceding control cycle continues as long as the thermistor positioned in the air space between the outer and inner reflectors indicates that temperature is below about 440F. If however, the temperature exceeds about 440F, radiant energy source 166 is energized at a lower power level (in this case 1,250 watts) when a sheet of support material 34 enters fusing apparatus 60. in addition thereto, auxiliary heater 186 remains energized, As support material 34 exits fusing apparatus 60, the machine control logic de-energizes radiant energy source 166, while auxiliary heater 186 remains energized. Fuser 60 is described in greater detail in co-pending application Ser. No. 300,531, filed in 1972, the disclosure of which is hereby incorporated into the present application.

In recapitulation, the electrophotographic printing machine depicted in FIG. 1 is adapted to create a black and white copy or a color copy from an original document. In operation, a black and white copy may be created by projecting a non-color filtered light image of the origianl document onto the charged photoconductive surface to create an electostatic latent image thereon corresponding thereto. The electrostatic latent image is developed with a magnetic brush developer unit containing black toner particles. Thereafter, the black toner powder image is transferred to a sheet of support material by a corona generating device cooperating with an electrically biased transfer roll having a sheet of support material secured thereto. The sheet of support material is stripped from the transfer roll and advanced to a fuser where the black toner powder image is permanently affixed thereto. Subsequently, the support material is advanced by conveyors to a catch tray where the operator may remove the black and white copy from the printing machine. When a color copy is being reproduced, the light image is color filtered to create a single color electrostatic latent image on the photoconductive surface. The single color electrostatic latent image is developed by a magnetic brush developer unit containing toner particles complementary in color to the filtered light image. For example, an electrostatic latent image corresponding to a red filtered light image is developed with cyan toner particles, whereas an electrostatic latent image corresponding to a cyan light image is developed with red toner particles. Once again, the toner powder image is transferred from the photoconductive member to the sheet of support material by a corona generating device cooperating with an electrically biased transfer roll having the sheet of support material secured thereto. Contra to the black and white process, the foregong process is repeated for a second single color electrostatic latent image. Hence, if initially a cyan light image is projected onto the photoconductive surface and red toner particles transferred to the support material, the next successive image will be a red light image wherein cyan toner particles will be transferred to the support material in superimposed registration with the red toner particles. After the pair of toner powder imaes has been transferred to the sheet of support material, the sheet of support material is stripped from the transfer roll and advanced to a fuser where the multilayered toner powder image is permanently affixed thereto. Thereafter, the sheet of support material is advanced by conveyors to a catch tray where the color copy may be removed by the machine operator. It should be noted that in the foregoing color process, black is created by a combination of cyan and red and is not created by utilization of black toner particles. While the invention has been described in connection with red and cyan toner particles, one skilled in the art will appreciate that the invention is not necessarily so limited and that yellow and blue toner particles or magenta in green toner particles may be used in lieu thereof with the corresponding color filter therefore.

Hence, in the color electrophotographic printing machine described heretofore a single pass black and white copy may be created as well as a multi-pass color copy simply by having the machine operator actuate the appropriate mechanisms by depressing the selected buttons.

Thus, it is apparent that there has been provided, in accordance with the present invention, an electrophotographic printing machine that fully satisfies the objects, aims, and advantages set forth above. While this invention has been disclosed in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.

What is claimed is:

1. An electrophotographic printing machine, including:

a photoconductive member;

means for charging said photoconductive member to a substantially uniform level;

means for exposing said charged photoconductive member to a light image recording an electrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image;

means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing means being arranged to develop the electrostatic latent image corresponding to the non-color filtered light image with black toner particles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto, said developing means comprising first means for depositing black toner particles onto the non-color filtered electrostatic latent image recorded on said photoconductive members, first means for actuating said toner particle depositing means in response to the non-color filtered electrostatic, latent image advancing to a predetermined location, whereby said first toner particle depositing means moves from an inoperative position spaced from the non-color filtered electrostatic latent image to a position adjacent thereto and in operative communication therewith, and first biasing means for resiliently urging said first toner depositing means from the position adjacent the non-color filtered electrostatic latent image to an inoperative position spaced therefrom;

means for transferring the toner powder image adhering to the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and

' means for fusing the toner powder image to the sheet of support material.

2. A printing machine as recited in claim 1, wherein said charging means includes:

an elongated shield defining an open-ended chamber;

a pair of spaced, substantially parallel conductive coronode wires mounted in said shield, said pair of coronode wires extending substantially in a longitudinal direction along the length of said shield; and

a plurality of spaced, substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of said coronode wires being disposed in the chamber therebeneath and the other of said coronde wires being disposed in the unenclosed portion of the chamber of said shield.

3. A printing machine as recited in claim 2, wherein said charging means further includes:

a wiper member positioned within said shield contacting said pair of coronode wires and the interior surface of said grid wires opposed from said pair coronode wires; and

means for moving said wiper member in substantially a longitudinal direction along the length of said coronode wires and said grid wires.

4. A printing machine as recited in claim 1, wherein said exposing means includes:

a light source arranged to illuminate an original document disposed in the printing machine; and

lens means for receiving the light rays from the origianl document to form a light image thereof.

16 5. A printing machine as recited in claim 4, wherein said exposing means further includes means, disposed in the path of the light image, for filtering the light image to produce a single color light image.

6. A printing machine as recited in claim 5, wherein said filtering means includes:

a cyan filter adapted to be interposed into the light image path to transmit a cyan light image therethrough; and

a red filter adapted to be interposed into the light image path to transmit red light image therethrough.

7. A printing machine as recited in claim 1, wherein said first toner depositing means includes:

a developer housing defining a chamber storing a developer mix comprising carrier granules and black toner particles;

conveyor means mounted for movement within the chamber of said developer housing and arranged to move the developer mix from a first region to an intermediate region;

rotary diven transport means mounted within the chamber of said developer housing and arranged to move the developer mix from the intermediate region to a second region for discharge thereat;

rotary driven developer means mounted within the chamber of said developer housing closely proximate to said transport means for receiving the tie veloper mix therefrom and arranged to deposit black toner particles onto the non-color filtered electrostatic latent image when in operative communciation therewith; and

means for driving said conveyor means such that the reaction torque to the driving moment applied to said conveyor means pivots said developer housing disposing said developer means adjacent the noncolor filtered elecrostatic latent image in operative communication therewith.

8. A printing machine as recited in claim 7, wherein:

said transport means includes a first tubular membe of non-magnetic material, and first magnetic means fixably disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and

said developer menas includes a second tubular member of non-magnetic material, and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member.

9. An electrophotographic printing machine, including:

a photoconductive member;

means for charging said photoconductive member to a substantially uniform level;

means for exposing said charged photoconductive member to a light image recording an electrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image;

means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing means being arranged to develop the electrostatic latent image corresponding to the non-color filtered light image with black tonerparticles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto, said developing means comprising second means for depositing toner particles complementary in color to the color filtered light image onto the color filtered electrostatic latent image recorded on said photoconductive member, second means for actuating said second toner particle depositing means in response to the color filtered electrostatic latent image advancing to a predetermined location, whereby said second toner particle depositing means imoves from an inoperative position spaced from the color filtered electrostatic latent image to a position adjacent thereto and in operative communication therewith, and second biasing means for resiliently urging said second toner depositing means from the position adjacent the color filtered electrostatic latent image to an inoperative position spaced therefrom;

means for transferring the toner powder image adhering to the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and

means for fusing the toner powder image to the sheet of support material.

10. A printing machine as recited in claim 9, wherein said second toner depositing means includes:

a developer housing defining a chamber storing a developer mix comprising carrier granules and toner particles complementary in color to the color filtered light image; and

conveyor means mounted for movement within the chabmer of said developer housing and arranged to move the developer mix from a first region to an intermediate region;

rotary driven transport means mounted within the A chamber of said developer housing and arranged to move the developer mix from the intermediate region to a second region for discharge thereat;

rotary driven developer means mounted within the chamber of said developer housing closely proximate to said transport means for receiving the developer mix therefrom and arranged to deposit the colored toner particles onto the color filtered electrostatic latent image when in operative communication therewith; and

means for driving said conveyor means such that the reaction torque to the driving moment applied to said conveyor means pivots said developer housing disposing said developer means adjacent the color filtered electrostatic latent image in operative communication therewith.

11. A printing machine as recited in claim 10,

wherein:

said transport means includes a first tubular member of non-m agnetic material, and first magnetic means fixably disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and

said developer means includes a second tubular member of non-magnetic material, and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member.

12. A printing machine as recited in claim 1, wherein said transferring means includes:

corona generating means disposed adjacent said photoconductive member and adapted to apply an alternating charge potential to said photoconductive member pre-conditioning the toner particles 5 thereon to readily facilitate the transfer therefrom; a transfer member operatively associated with said corona generating means and having the sheet of support material secured releasably thereto; and

means for electrically biasing said transfer member to a potential of sufficient magnitude and polarity to attract the pre-conditioned toner particles from the electrostatic latent image recored on said photoconductive member to the sheet of support mate- 5 rial secured thereto.

13. A printing machine as recited in claim 12, wherein said corona generating means includes:

an elongated shield defining an open-ended chamber;

and a corona discharge elecrode mounted in the chamber of said shield and arranged therein to generate ions for charging the toner particles deposited on the electrostatic latent image recorded on said photoconductive member. 2 14. A printing machine as recited in claim 12,

wherein said transfer member includes:

a cylindrical core of electrically conductive material; a first layer of resilient material entrained about said cylindrical core and being substantially in contact therewith; and

a scond layer of resilient material entrained about said first layer of resilient material and being substantially in contact therewith.

15. A printing machine as recited in claim 1, wherein said fusing means includes:

means for transporting the sheet of support material with the toner powder image deposited on one surface thereof along a path of movement, said transporting means being arranged to be in substantial contact with the other surfaces of the support material; means for heating said transporting means; and a radiant energy source arranged to be in thermal communication with a sheet of support material for supplying the energy output thereof onto .the sheet of support material being moved with the toner powder image thereon by said transporting means along the path of movement for affixing substantially permanently the toner powder image to the sheet of support material.

16. An electrophotographic printing machine, in-

cluding:

a photoconductive member;

means for charging said photoconductive member to a substantially uniform level;

means for exposing said charged photoconductive member to a light image recording an elecrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image;

means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing menas being arranged todevelop the electrostatic latent image corresponding to the non-color filtered light image with black toner particles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto;

means for transferring the toner powder image adhering to the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and

means for fusing the toner powder image to the sheet of support material, said fusing comprising a lower housing member defining an interior open-ended chamber, a frame member mounted removably in the chamber of said lower housing member, a plurality of rollers mounted rotatably on said frame member, said rollers being positioned spaced from one another and having the axes of rotation thereof substantially parallel to one another, an endless belt member having a plurality of apertures therein, said belt member being entrained about said rollers, means for removing air from the chamber of said lower housing to secure releasably the sheet of support material to the exterior surface of said belt member, means for heating said belt member, and a radiant energy source arranged to be in thermal communication with a sheet of support material for supplying the energy output thereof onto the sheet of support material moved with the toner powder image thereon by said belt member along the path of movement for affixing substantially permanently the toner powder image to the 2 0 sheet of support material. a

17. A printing machine as recited in claim 16,

wherein said heating means includes:

a plate member mounted in the open end of the chamber of said lower housing member interposed between said rollers and substantially contacting the interior surface of said belt member; and

at least one resistant heating element disposed in the chamber of said lower housing member, said heating element being positioned in the path of move ment of the air being removed from the chamber heating the air which heats said belt member.

18. A printing machine as recited in claim 16,

wherein said radiant energy source includes:

a cover mounted on said lower housing member and defining with said lower housing member a passageway enabling said endless belt member to move the sheet of support material therethrough;

at least one radiant heat strip secured to said cover member, said heat strip being configured to furnish substantially uniform radiation across the sheet of support material; and

reflecting means interposed between said cover member and said radiant heat strip directing the energy output therefrom onto the sheet of support material to permanently affix the toner powder image thereto. 

1. An electrophotographic printing machine, including: a photoconductive member; means for charging said photoconductive member to a substantially uniform level; means for exposing said charged photoconductive member to a light image recording an electrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image; means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing means being arranged to develop the electrostatic latent image corresponding to the non-color filtered light image with black toner particles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto, said developing means comprising first means for depositing black toner particles onto the non-color filtered electrostatic latent image recorded on said photoconductive members, first means for actuating said toner particle depositing means in response to the non-color filtered electrostatic latent image advancing to a predetermined location, whereby said first toner particle depositing means moves from an inoperative position spaced from the non-color filtered electrostatic latent image to a position adjacent thereto and in operative communication therewith, and first biasing means for resiliently urging said first toner depositing means from the position adjacent the non-color filtered electrostatic latent image to an inoperative position spaced therefrom; means for transferring the toner powder image adhering to The electrostatic latent image recorded on said photoconductive member to a sheet of support material; and means for fusing the toner powder image to the sheet of support material.
 2. A printing machine as recited in claim 1, wherein said charging means includes: an elongated shield defining an open-ended chamber; a pair of spaced, substantially parallel conductive coronode wires mounted in said shield, said pair of coronode wires extending substantially in a longitudinal direction along the length of said shield; and a plurality of spaced, substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of said coronode wires being disposed in the chamber therebeneath and the other of said coronde wires being disposed in the unenclosed portion of the chamber of said shield.
 3. A printing machine as recited in claim 2, wherein said charging means further includes: a wiper member positioned within said shield contacting said pair of coronode wires and the interior surface of said grid wires opposed from said pair coronode wires; and means for moving said wiper member in substantially a longitudinal direction along the length of said coronode wires and said grid wires.
 4. A printing machine as recited in claim 1, wherein said exposing means includes: a light source arranged to illuminate an original document disposed in the printing machine; and lens means for receiving the light rays from the origianl document to form a light image thereof.
 5. A printing machine as recited in claim 4, wherein said exposing means further includes means, disposed in the path of the light image, for filtering the light image to produce a single color light image.
 6. A printing machine as recited in claim 5, wherein said filtering means includes: a cyan filter adapted to be interposed into the light image path to transmit a cyan light image therethrough; and a red filter adapted to be interposed into the light image path to transmit red light image therethrough.
 7. A printing machine as recited in claim 1, wherein said first toner depositing means includes: a developer housing defining a chamber storing a developer mix comprising carrier granules and black toner particles; conveyor means mounted for movement within the chamber of said developer housing and arranged to move the developer mix from a first region to an intermediate region; rotary diven transport means mounted within the chamber of said developer housing and arranged to move the developer mix from the intermediate region to a second region for discharge thereat; rotary driven developer means mounted within the chamber of said developer housing closely proximate to said transport means for receiving the developer mix therefrom and arranged to deposit black toner particles onto the non-color filtered electrostatic latent image when in operative communciation therewith; and means for driving said conveyor means such that the reaction torque to the driving moment applied to said conveyor means pivots said developer housing disposing said developer means adjacent the non-color filtered elecrostatic latent image in operative communication therewith.
 8. A printing machine as recited in claim 7, wherein: said transport means includes a first tubular membe of non-magnetic material, and first magnetic means fixably disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and said developer menas includes a second tubular member of non-magnetic material, and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member.
 9. An electrophotographic printing machine, including: a photoconductive member; MEANS for charging said photoconductive member to a substantially uniform level; means for exposing said charged photoconductive member to a light image recording an electrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image; means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing means being arranged to develop the electrostatic latent image corresponding to the non-color filtered light image with black toner particles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto, said developing means comprising second means for depositing toner particles complementary in color to the color filtered light image onto the color filtered electrostatic latent image recorded on said photoconductive member, second means for actuating said second toner particle depositing means in response to the color filtered electrostatic latent image advancing to a predetermined location, whereby said second toner particle depositing means moves from an inoperative position spaced from the color filtered electrostatic latent image to a position adjacent thereto and in operative communication therewith, and second biasing means for resiliently urging said second toner depositing means from the position adjacent the color filtered electrostatic latent image to an inoperative position spaced therefrom; means for transferring the toner powder image adhering to the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and means for fusing the toner powder image to the sheet of support material.
 10. A printing machine as recited in claim 9, wherein said second toner depositing means includes: a developer housing defining a chamber storing a developer mix comprising carrier granules and toner particles complementary in color to the color filtered light image; and conveyor means mounted for movement within the chabmer of said developer housing and arranged to move the developer mix from a first region to an intermediate region; rotary driven transport means mounted within the chamber of said developer housing and arranged to move the developer mix from the intermediate region to a second region for discharge thereat; rotary driven developer means mounted within the chamber of said developer housing closely proximate to said transport means for receiving the developer mix therefrom and arranged to deposit the colored toner particles onto the color filtered electrostatic latent image when in operative communication therewith; and means for driving said conveyor means such that the reaction torque to the driving moment applied to said conveyor means pivots said developer housing disposing said developer means adjacent the color filtered electrostatic latent image in operative communication therewith.
 11. A printing machine as recited in claim 10, wherein: said transport means includes a first tubular member of non-magnetic material, and first magnetic means fixably disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and said developer means includes a second tubular member of non-magnetic material, and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member.
 12. A printing machine as recited in claim 1, wherein said transferring means includes: corona generating means disposed adjacent said photoconductive member and adapted to apply an alternating charge potential to said photoconductive member pre-conditioning the toner particles thereon to readily facilitate the transfer therefrom; a transfer member operatively associated with said corona generating means and having the sheet of suPport material secured releasably thereto; and means for electrically biasing said transfer member to a potential of sufficient magnitude and polarity to attract the pre-conditioned toner particles from the electrostatic latent image recored on said photoconductive member to the sheet of support material secured thereto.
 13. A printing machine as recited in claim 12, wherein said corona generating means includes: an elongated shield defining an open-ended chamber; and a corona discharge elecrode mounted in the chamber of said shield and arranged therein to generate ions for charging the toner particles deposited on the electrostatic latent image recorded on said photoconductive member.
 14. A printing machine as recited in claim 12, wherein said transfer member includes: a cylindrical core of electrically conductive material; a first layer of resilient material entrained about said cylindrical core and being substantially in contact therewith; and a scond layer of resilient material entrained about said first layer of resilient material and being substantially in contact therewith.
 15. A printing machine as recited in claim 1, wherein said fusing means includes: means for transporting the sheet of support material with the toner powder image deposited on one surface thereof along a path of movement, said transporting means being arranged to be in substantial contact with the other surfaces of the support material; means for heating said transporting means; and a radiant energy source arranged to be in thermal communication with a sheet of support material for supplying the energy output thereof onto the sheet of support material being moved with the toner powder image thereon by said transporting means along the path of movement for affixing substantially permanently the toner powder image to the sheet of support material.
 16. An electrophotographic printing machine, including: a photoconductive member; means for charging said photoconductive member to a substantially uniform level; means for exposing said charged photoconductive member to a light image recording an elecrostatic latent image thereon, said exposing means being adapted to form color filtered light images and a non-color filtered light image; means for developing the electrostatic latent image recorded on said photoconductive member with toner particles, said developing menas being arranged to develop the electrostatic latent image corresponding to the non-color filtered light image with black toner particles and the electrostatic latent image corresponding to the color filtered light images with toner particles complementary in color thereto; means for transferring the toner powder image adhering to the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and means for fusing the toner powder image to the sheet of support material, said fusing comprising a lower housing member defining an interior open-ended chamber, a frame member mounted removably in the chamber of said lower housing member, a plurality of rollers mounted rotatably on said frame member, said rollers being positioned spaced from one another and having the axes of rotation thereof substantially parallel to one another, an endless belt member having a plurality of apertures therein, said belt member being entrained about said rollers, means for removing air from the chamber of said lower housing to secure releasably the sheet of support material to the exterior surface of said belt member, means for heating said belt member, and a radiant energy source arranged to be in thermal communication with a sheet of support material for supplying the energy output thereof onto the sheet of support material moved with the toner powder image thereon by said belt member along the path of movement for affixing substantially permanently the toner powder image to the sheet of support material.
 17. A printinG machine as recited in claim 16, wherein said heating means includes: a plate member mounted in the open end of the chamber of said lower housing member interposed between said rollers and substantially contacting the interior surface of said belt member; and at least one resistant heating element disposed in the chamber of said lower housing member, said heating element being positioned in the path of movement of the air being removed from the chamber heating the air which heats said belt member.
 18. A printing machine as recited in claim 16, wherein said radiant energy source includes: a cover mounted on said lower housing member and defining with said lower housing member a passageway enabling said endless belt member to move the sheet of support material therethrough; at least one radiant heat strip secured to said cover member, said heat strip being configured to furnish substantially uniform radiation across the sheet of support material; and reflecting means interposed between said cover member and said radiant heat strip directing the energy output therefrom onto the sheet of support material to permanently affix the toner powder image thereto. 